sql server – How to fix error recording sp_whoisactive results to table?

Have a sql agent job modeled from here that uses sp_whoisactive to capture results to a table. 99% it works fine but every now and then the sql agent job will fail with this error:

Warning: Null value is eliminated by an aggregate or other SET operation. (SQLSTATE 01003) (Message 8153) Violation of PRIMARY KEY constraint 'PK__#ADDF8B9__69B13FDC8C10EA7F'. Cannot insert duplicate key in object 'dbo.@blockers'. The duplicate key value is (623). (SQLSTATE 23000) (Error 2627) The statement has been terminated. (SQLSTATE 01000) (Error 3621) Warning: Null value is eliminated by an aggregate or other SET operation. (SQLSTATE 01003) (Message 8153) Warning: Null value is eliminated by an aggregate or other SET operation. (SQLSTATE 01003) (Message 8153). The step failed.

Here is table def

USE (Maint)
GO

/****** Object:  Table (dbo).(WhoIsActive)    ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE (dbo).(WhoIsActive)(
    (dd hh:mm:ss.mss) (varchar)(8000) NULL,
    (session_id) (smallint) NOT NULL,
    (sql_text) (xml) NULL,
    (sql_command) (xml) NULL,
    (login_name) (nvarchar)(128) NOT NULL,
    (wait_info) (nvarchar)(4000) NULL,
    (tran_log_writes) (nvarchar)(4000) NULL,
    (CPU) (varchar)(30) NULL,
    (tempdb_allocations) (varchar)(30) NULL,
    (tempdb_current) (varchar)(30) NULL,
    (blocking_session_id) (smallint) NULL,
    (reads) (varchar)(30) NULL,
    (writes) (varchar)(30) NULL,
    (physical_reads) (varchar)(30) NULL,
    (query_plan) (xml) NULL,
    (used_memory) (varchar)(30) NULL,
    (status) (varchar)(30) NOT NULL,
    (tran_start_time) (datetime) NULL,
    (open_tran_count) (varchar)(30) NULL,
    (percent_complete) (varchar)(30) NULL,
    (host_name) (nvarchar)(128) NULL,
    (database_name) (nvarchar)(128) NULL,
    (program_name) (nvarchar)(128) NULL,
    (start_time) (datetime) NOT NULL,
    (login_time) (datetime) NULL,
    (request_id) (int) NULL,
    (collection_time) (datetime) NOT NULL
) ON (PRIMARY) TEXTIMAGE_ON (PRIMARY)
GO

What is causing this error?

sp_whoisactive version = v11.11.